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Finally made a real part in the CNC mill !!!!!

We finally got around to making a ( what I consider ) real part. It's a timing cover plate for the Ford pulling tractor. There is a lot of stuff to buy or make. When you start off in the CNC machinist realm. I still consider my self a beginner and need to make a lot of fixtures. I can see down the road that we will have tons of fixtures and one off doodads. The chuck is barrowed off a indexer and we made the back plate. The finish is good but not perfect. Still need some more practice with Bob Cam. I thought it was going to make a finish pass on the pocket and it did. But just on the side wall. The recommend speeds are to slow for the cutters also. That will be a some thing I have to work out. The top of the cover was the same bad finish (speeds to slow). We reran the final pass and bumped the speed to 4000 rpm and .0125 cut. The face mill produced good finish. Just need to play with it some more and maybe we can get the lines out. I used peck milling to do the roughing.

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That looks about normal, if you go to Cimco http://www.cimco.com/download.php3 and down load the free feed and speed calculator life with the CNC will be much more rewarding. Chip loading is the key parameter along with sfm are the best way to go. In 6061 alum. with a 4 flute 3/8" carbide usually gives a low Ra finish around 3300 rpm, but, alot depends on your set up and length sticking out the nose of the holder. Niagra Cutter has extremely good data on depth of cut relative to cutter diameter, and their "starting point" is pretty close for the average VMC running on linear bearings.

You should be running all EM's under about 5/8" at 6000 RPM in aluminum, just adjust the feed rate for the recommended chip load. The face mill should also be run at 6000 RPM and 70 to 100 IPM. On my Fadal I run a 3.5" face mill at 7500 RPM and 120 IPM in aluminum. I sold a TM-1 to Harold V over on the Chaski board. It had a 6000 RPM spindle too, almost always ran at 6000 RPM.

Also loose the Tin coated EM's they are not good in aluminum. 3 flute is good for roughing and some finishing operations. 4 flute is good for finishing with a fairly light cut, .010" to .020". Always climb cut. EM's will last way longer on your CNC mill then a manual mill so spend the money for good ones.